Answer:
a) Independent 2 sample t-test
Explanation:
The main purpose of a t-test is to determine if there is a significant difference between the means of two groups. The company should use the independent 2 sample test, because this one tests whether the difference between the means of two independent populations is equal to a target value.
In this case, it will test the difference between the favorable ratings for a senator poll, comparing the opinnion of two independent groups, which are Democrats and Republicans.